Heat exchanger

ABSTRACT

A heat exchanger serves to cool a cooling medium, which in turn is intended to cool an electronic component ( 76 ). The heat exchanger has an inflow ( 64 ) for delivery of hot coolant, and an outflow ( 68 ) for discharge of coolant cooled in the heat exchanger. An equalizing vessel ( 30 ) is joined to the heat exchanger to form one module. The vessel serves to equalize changes in coolant volume. The equalizing vessel ( 30 ) is closed off by a flexible membrane ( 54 ) which follows such changes in volume. The equalizing vessel ( 30 ) is implemented as a component of the coolant circuit. One part of the equalizing vessel is implemented as a component of the inflow ( 64 ) and another part as a component of the outflow ( 68 ), which parts are in liquid communication with one another via a switchback path through passages ( 22 ) within the heat exchanger ( 20 ) that is implemented in double-flow fashion.

CROSS-REFERENCE

This application is a section 371 of PCT/EP05/014 154, filed 31 Dec.2005, published 24 Aug. 2006 as WO-2006-087031-A.

FIELD OF THE INVENTION

The invention relates to a heat exchanger for cooling a cooling medium,in particular in an electrical/electronic device.

BACKGROUND

In a closed cooling system filled with a coolant, temperature changes aswell as permeation, for example through tube walls, result in a changein the volume of the coolant. Some compensation or equalization for thiscoolant volume change, that ensures that no, or only small, pressurechanges occur in the system, must be found.

Such changes in volume can be buffered by means of a so-calledequalizing vessel. This causes additional costs, however, and alsoincreases the risk of cooling medium leaking out.

An important problem in the context of heat exchangers for electronicdevices is that their exact operating orientation is not known, apriori. This is true not least for transportation to the customer, sincesuch cooling systems are already filled with cooling medium at themanufacturer's premises, and the orientation they will assume duringtransport cannot be predicted. The same is true for utilization invehicles of all kinds (aircraft, ships, land vehicles, vehicles in aweightless state). Operating reliability must therefore be guaranteed inall conceivable operating orientations. If liquid were to mix with gasin the cooling circuit, reliable operation of a circulating pump wouldthen no longer be guaranteed, with the result that cooling performancemight rapidly decrease. This would then very quickly cause theelectronic component being cooled either to switch itself off, or to bedestroyed by the increase in temperature.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to make available a novelheat exchanger.

According to the invention, this object is achieved by forming atwo-part equalizing vessel, incorporating a flexible membrane whichdynamically adapts to changes in coolant volume, as part of a heatexchanger, one part being implemented as part of the inflow and one partbeing implemented as part of the outflow of the heat exchanger.

A compact and economical arrangement is thereby achieved. The risk thatcooling medium may leak out and cause damage to the electronics isreduced. The at least one flexible membrane or diaphragm also causes theinternal volume of the cooling circuit to be adapted automatically tothe variable volume of the cooling medium that is present in the coolingcircuit, so that the creation of gas bubbles in the cooling medium isprevented, regardless of the operating orientation of the heatexchanger. This makes possible reliable cooling even after the heatexchanger has temporarily assumed an unusual operating orientation, e.g.during transport.

A particularly preferred embodiment of such a heat exchanger is to joina heat exchanger to an equalizing vessel in a single module,incorporating a coolant filter at an interface therebetween. Itprevents, at very low cost, problems and damage due to contaminants inthe cooling medium.

The preferred refinement, according to which the filter is a plasticpart directly attached to a housing of the equalizing vessel, yields acompact, robust, and cost-saving design.

BRIEF FIGURE DESCRIPTION

Further details and advantageous refinements of the invention areevident from the exemplifying embodiments, in no way to be understood aslimitations of the invention, that are described below and depicted inthe drawings.

FIG. 1 is a schematic depiction showing, by way of example, a heatexchanger according to the invention and its arrangement in a coolingcircuit;

FIG. 2 is an enlarged depiction of detail II of FIG. 1;

FIG. 3 is an enlarged depiction of detail III of FIG. 1;

FIG. 4 is an enlarged depiction of detail IV of FIG. 1;

FIG. 5 is a three-dimensional depiction, shown partially in section, ofan exemplifying embodiment according to the invention;

FIG. 6 is a depiction analogous to FIG. 5, viewed in the direction ofarrow VI of FIG. 5;

FIG. 7 is a three-dimensional depiction of the membrane used in the heatexchanger according to FIGS. 1 to 6 and of the spring element joined toit; and

FIG. 8 shows a second exemplifying embodiment of the invention;

FIG. 9 is an overview of a second exemplifying embodiment of theinvention;

FIG. 10 is a section viewed along line X-X of FIG. 11;

FIG. 11 is a top view looking in the direction of arrow XI of FIG. 10;

FIG. 12 is an enlarged depiction of detail XII of FIG. 10;

FIG. 13 is a three-dimensional depiction of a heat exchanger 130′ thatis equipped with an integrated large-area filter;

FIG. 14 is an enlarged depiction of detail XIV of FIG. 13;

FIG. 15 is a section through the upper part of heat exchanger 120′depicted in FIG. 13;

FIG. 16 is a section analogous to FIG. 15; in this variant, filter 170is arranged and mounted differently than in FIG. 15; and

FIG. 17 is a sectioned detail depiction of the filter and the seal fromFIG. 16.

DETAILED DESCRIPTION

FIG. 1 schematically shows a heat exchanger 20. The latter has, in knownfashion, flat cooling tubes 22 through which a cooling medium 24 flowsduring operation, and which are joined in thermally conductive fashionto cooling plates 26 arranged in a zigzag shape.

The spaces between the flat tubes 22 are closed off at the top inliquid-tight fashion by closure panels 28, thus creating an upper tank30 that is subdivided by a vertical partition 32 into an inflow-sidechamber 34 and an outflow-side chamber 36.

The spaces between tubes 22 are likewise closed off at the bottom inliquid-tight fashion by closure panels 38, so that a lower tank 40 isformed there.

Upper tank 30 is joined in liquid-tight fashion to heat exchanger 20 bymeans of a crimped join 44. It has an upper wall 46 (FIG. 3) that isimplemented here integrally with partition 32. Apertures are located insaid wall, namely an aperture 48 above outflow-side space 36 and anaperture 50 above inflow-side space 34.

These apertures 48, 50 are hermetically closed off in liquid-tightfashion on their upper sides by a flexible membrane 54 on which rests aflat spring arrangement 56 made of non-corroding spring steel. Thisspring arrangement 56 is joined to membrane 54, for example, byvulcanization. For this purpose, spring arrangement 56 can also bevulcanized into membrane 54 in order to protect it particularly wellfrom corrosion.

Diaphragm 54 and spring arrangement 56 are retained in fluid-tightfashion at their outer rim by the rim 58 of a cover 60. They arelikewise retained at the center by a strut 61 of cover 60 (cf. FIG. 3).Air or an inert gas, e.g. nitrogen, is present in space 62 between cover60 and membrane 54.

Upper tank 30 has an inflow 64, and through the latter cooling medium(hereinafter “coolant” for short) 24 flows in the direction of an arrow66 to inflow-side chamber 34. From there, it flows downward throughpassages or tubes 22 located there to lower tank 40, and from the latterthrough the left-hand (in FIG. 1) tubes 22 upward to outflow-sidechamber 36, i.e. the flow follows a switchback or two-direction-flowpath. The flow direction can, of course, be the reverse in some cases.

From there the cooling medium flows through an outflow 68, in thedirection of an arrow 70, to a heat sink 74 that is joined in thermallyconductive fashion to an electronic component 76 that is arranged on acircuit board 78 and is supplied with current through the latter.

The cooling medium is heated in heat sink 74, and the heated coolingmedium is delivered back to inflow 66 by means of a circulating pump 82driven by an electric motor 80.

Heat exchanger 20 is cooled by air by means of a fan 84, this beingindicated only very schematically.

FIGS. 5 to 7 show the construction of spring arrangement 56. The latteris formed by the fact that a left-hand spiral-shaped aperture 90 and aright-hand spiral aperture 92 are incorporated into a thin sheet ofspring steel, thereby creating at the left a larger spiral spring 94that is associated with larger chamber 36, and at the right a smallerspiral spring 96 that is associated with smaller chamber 34.

Chambers 34, 36 are filled with cooling medium 24 up to membrane 54.When said medium expands, membrane 54 bulges upward above apertures 48,50; springs 94, 96 prevent membrane 54 from protruding and being damagedat individual locations.

When cooling medium 24 contracts, membrane 54 bulges downward throughapertures 48, 50; here again, springs 94, 96 ensure uniform deflection.

A reliably functioning equalizing vessel 30 is thereby obtained withlittle complexity.

In FIG. 7 the deflections described are depicted symbolically by arrows100, 102 (upward) and 104, 106 (downward).

FIG. 8 shows an equalizing vessel 110 that has only a single connector112 through which coolant flows in or out during operation. Vessel 110has at the bottom a cup 114 at whose upper end is provided an outwardlyprojecting flange 116 in which an annular groove 118 is located.Engaging into the latter is a sealing bead 120 belonging to an elasticmembrane 121, which bead is pressed sealingly into annular groove 118 bya cover 122. The mounting of cover 122 on cup 114 is not depictedbecause it is known.

Elastic membrane 121 is pressed downward at its center, in the mannershown, by a plunger 126 acted upon by a spring 124. Plunger 126 projectsat the top through an opening 128 in cover 122 and is equipped therewith a scale 130 for pressure indication. This plunger 126 facilitatesventing, e.g. after a repair. Here as well, the space beneath membrane121 is filled completely with coolant, i.e. with no air bubbles.

FIGS. 9 to 12 show a second, preferred exemplifying embodiment of theinvention. Parts identical or functioning identically to those in FIGS.1 to 8 are usually labeled with the same reference characters astherein, and are not described again.

FIG. 9 is an overview image analogous to FIG. 1. The heated coolingfluid from heat absorber 74 is delivered via a conduit 66 to inflow 64of heat exchanger 120, where it is cooled. From outflow 68, it flows viaa conduit 70 to a unit 140. The latter contains a circulating pump forthe cooling fluid (analogous to pump 82 of FIG. 1) and a fan (analogousto fan 84 of FIG. 1) to generate cooling air for heat exchanger 120. Incontrast to FIG. 1, the fan and the circulating pump are driven by thesame electric motor (cf. e.g. the Assignee's WO2004/031588A1, ANGELIS etal., whose U.S. phase is U.S. Ser. No. 10/527,471, published asUS-2006-032 625-A.

Cooling channels 22, cooling plates 26, etc. are configured in the sameway as in the first exemplifying embodiment according to FIGS. 1 to 8.

As shown particularly well by FIG. 12, heat exchanger tank 130 ismanufactured from a thermoplastic by injection molding.

This tank 130 has an inwardly projecting flange 48, and in a secondinjection-molding step a flexible membrane 154 made of TPE(thermoplastic elastomer) is molded, as a soft component, onto the upperside of this flange 48. This method is also referred to as two-componentinjection molding. The seam is labeled 155.

Thermoplastic silicone elastomers that are made up of a two-phase blockcopolymer (polydimethylsiloxane/urea copolymer) are preferably suitablefor membrane 154. A TPE-A (polyether block amide) can also be used ifapplicable.

Because the strength of the join between the thermoplastic material oftank 130 and the molded-on TPE of membrane 154 is not very high in theregion of joining seam 156, cover 60 is used as additional security;this has a downwardly projecting portion 158′ that rests with pressureon the welded-on rim of membrane 154 in region 156, i.e. along theentire periphery of membrane 154.

For this purpose, outer rim 158 of cover 60 is joined to upper rim 160of tank 130, e.g. by laser welding, adhesive bonding, bolting, or by wayof a latching join. FIG. 12 shows a join by means of a notch 166 and aprojecting rim 168, which are joined by laser welding. Laser weldingresults, in space 162 between cover 60 and membrane 154, in an enclosedair cushion that braces membrane 154 toward the top and thereby relievesmechanical stress.

If too much oxygen diffuses into the cooling system through the plasticwalls, it oxidizes the corrosion inhibitors contained in the coolant andgas bubbles may form; this can result in malfunctions in the coolingsystem and in some cases even a failure of the cooling system. If toomuch coolant diffuses outward through the plastic walls, at some timeduring the required service life (often approx. 60,000 hours) there willbe too little coolant remaining in the system for it to continuefunctioning, and a failure then likewise occurs.

These requirements, in addition to the temperature and strength demands,limit the suitable materials.

Appropriate basic materials (hard components) for tank 130 are:polyphenylene oxide (PPO), glass-fiber reinforced; optionally alsopolypropylene (PP), likewise glass-fiber reinforced. Particularlysuitable on the basis of present knowledge, in view of the requirementof very low permeability for water, glycol, or another coolant outwardfrom the cooling circuit on the one hand, and for oxygen from outsideinto the coolant on the other hand, is polyphenylene sulfide (PPS),glass-fiber reinforced; or PA-HTN, a temperature-stabilized polyamide,likewise glass-fiber reinforced.

PA is very well suited for laser welding, PPS somewhat less so. PA istherefore preferred when suitable, including for price reasons.

What is achieved by means of the invention is that heat exchanger 120can simultaneously also work as an equalizing vessel to allow theequalization of changes in the volume of cooling liquid; such changesare inevitable during extended operation, and can also occur as a resultof temperature fluctuations.

FIG. 13 shows a heat exchanger 120′ having an integrated filter 170.According to FIG. 14, this filter 170 has filter openings 172 that, forexample, can be larger on inflow side 36 (on the right in FIG. 13) thanon outflow side 34, in order to achieve firstly coarse filtration andthen fine filtration. The portion of filter 170 that performs the coarsefiltration could also be referred to as a sieve.

Filter 170 can be made of metal or plastic, and according to FIG. 15 ismounted on the lower side of vessel 130′, e.g. using the two-componentinjection molding method.

FIG. 16 shows an alternative in which filter 170 is joined to seal 44 ato form one module. This can be achieved, for example, by vulcanization.Alternatively, and particularly economically, it is possible e.g. toinjection-embed filter 170 in TPE using the injection molding method. Inboth cases, assembly is simplified, and a very robust heat exchanger isobtained.

In the region of inflow 36, filter 170 filters cooling medium that flowsvia inlet 64 into vessel 130′ and from there downward into flat tubes 22of heat exchanger 20. Coarse dirt is thereby held back on the right sideof filter 170.

The cooling medium then flows through the left half of flat tubes 22from bottom to top, being filtered by the left half of filter 170 sothat coolant, which has been filtered twice, flows through outflow 68 topump 140 (FIG. 9).

This is important because pump 140 is very sensitive to contaminants inthe coolant, and therefore must be particularly well protected, sincecontaminants could cause pump 140 to seize.

From pump 140, the coolant flows (according to FIG. 9) to heat absorber74 and from there back to inlet 64.

The result of the large filter area, in the context of this innovativearrangement, is that the pressure drop at filter 170 becomes very low.

When a heat absorber that has been machined in chip-removing fashion isused, the machining chips that are created cannot be completely removedwithout reducing the efficiency of heat absorber 74.

In heat exchanger 20 as well, residual chips and dirt particles cannotbe avoided during the manufacturing process, but at best can be reducedby soldering it under vacuum and then thoroughly rinsing and cleaningit.

The entry of dirt into the coolant circuit, during filling with coolantand subsequent testing, likewise cannot be entirely avoided.

The consequence is that chips and dirt might clog the small-scalestructures in the heat absorber and thereby reduce efficiency. Thedanger also always exists that dirt particles may get into a narrow gapin pump 140 and thus cause blockage of the pump.

Such problems are eliminated by the invention. It is particularlyadvantageous that the invention yields a large filter area, and anadditional filter housing can thus be eliminated. In the liquid circuit,chips and dirt particles that become detached in the heat absorber andheat exchanger are reliably held back on the outflow side at filter 170before they flow into pump 140. The large filter area, relative to theamount of dirt that occurs, prevents clogging of the filter and anexcessive pressure drop in the cooling medium in the circuit.

The invention therefore eliminates the need to provide a separate filterhousing along with hose connections, thus reducing costs. In addition,no space is required for a separate filter housing and the requisitehose connections, enabling a compact design. Lastly, with the filterarranged as depicted (i.e. in the heat exchanger tank), chips thatbecome detached from heat absorber 74 and heat exchanger 20 cannot getinto pump 140, since the latter is arranged in the flow direction afterheat exchanger 20 and before heat absorber 74. At no other location inthe overall system, moreover, could the filter area be made so largewithout substantial additional cost. Clogging of the small-scalestructures of heat absorber 74 is therefore prevented or greatly reducedin simple fashion, as is blockage of circulating pump 140.

An equalization vessel that is separate from the heat exchanger could ofcourse also be manufactured using the same principle, for example if thevolume of the heat exchanger is limited for space reasons. In other waysas well, many variants and modifications are possible within the scopeof the present invention.

FIG. 17 is a sectioned detail depiction of filter 170 and seal 44 a ofFIG. 16. Upon installation of filter 170 into heat exchanger 20, seal 44a is preferably deformed in order to produce a good seal (cf. FIG. 16).

1. A heat exchanger for arrangement in a closed cooling circuit, which latter is filled during operation with a coolant operated in forced circulation, and serves to cool at least one electronic component (76), having an inflow (64) for delivery of hot coolant to the heat exchanger (20), having an outflow (68) for discharge of coolant cooled in the heat exchanger, and having an equalizing vessel (30; 130; 130′), joined to the heat exchanger to form one module, for equalizing changes in coolant volume, which equalizing vessel (30; 130; 130′) is closed off by a flexible membrane (54; 154) that follows such changes in volume, the equalizing vessel (30; 130; 130′) being implemented as part of a flow circuit of the coolant, and one part (34) of the equalizing vessel being implemented as a component of the inflow (64), and another part (36) as a component of the outflow (68), which parts are in liquid communication with one another through passages (22) within the heat exchanger (20).
 2. The heat exchanger according to claim 1, wherein a separate flexible membrane (54; 154) is associated with each of the parts of the heat exchanger.
 3. The heat exchanger according to claim 1, in which at least one filter (170) is provided for filtering the coolant.
 4. The heat exchanger according to claim 3, in which the at least one filter (170) is arranged between equalizing vessel (130′) and heat exchanger (20) in the flow circuit of the coolant.
 5. The heat exchanger according to claim 4, in which the at least one filter (170) is provided adjacent a location at which the coolant flows into a conduit (64) of the heat exchanger (20).
 6. The heat exchanger according to claim 4, wherein the at least one filter (170) is provided adjacent a location at which the coolant emerges from a conduit (66) of the heat exchanger (20).
 7. The heat exchanger according to claim 1, which is configured for operation with a circulating pump (140) upstream from which pump are arranged, in series, two filters (170) of which at least one is arranged between equalizing vessel (130′) and heat exchanger (20).
 8. The heat exchanger according to claim 7, wherein the filters (170) arranged in series are arranged in the equalizing vessel (130′) of the heat exchanger (20).
 9. The heat exchanger according to claim 1, wherein the equalizing vessel (30; 130; 130′) is joined to the heat exchanger (20) by a crimped join (44) to form one module.
 10. The heat exchanger according to claim 9, wherein a seal (44 a) is provided between equalizing vessel (30; 130; 130′) and heat exchanger.
 11. The heat exchanger according to claim 10, wherein the seal (44 a) is joined to the filter (170) to form a unitary element.
 12. The heat exchanger according to claim 11, wherein the seal (44 a) is joined to the filter (170) by one of injection-embedding and vulcanization.
 13. The heat exchanger according to claim 1, wherein the flexible membrane (54; 154) is braced, on its side facing away from the coolant, by at least one spring arrangement.
 14. The heat exchanger according to claim 13, wherein the at least one spring arrangement is implemented as a sheet-metal spring (56) that is subdivided into resilient portions by at least one aperture (90; 92).
 15. The heat exchanger according to claim 14, wherein at least parts of the sheet-metal spring (56) are joined to the flexible membrane (54).
 16. The heat exchanger according to claim 14, wherein the aperture (90, 92) of the sheet-metal spring (56) associated with the one spring (94, 96) is implemented as an interconnected aperture.
 17. The heat exchanger according to claim 16, wherein the interconnected aperture of the sheet-metal spring (56) is implemented as a spiral (90, 92).
 18. The heat exchanger according to claim 1, wherein the equalizing vessel comprises a cover (60) having a rim (58, 158), which rim abuts against the rim of the flexible membrane (54; 154) and clamps the aforesaid rim (58, 158) between itself and an element (48) of the equalizing vessel (130).
 19. The heat exchanger according to claim 18, wherein the rim of the flexible membrane (54; 154) comprises a directly attached join (155) to an element (48) of the equalizing vessel (30; 130; 130′).
 20. The heat exchanger according to claim 1, wherein a space (62; 162) hermetically closed off is provided on a side of the flexible membrane (54; 154) located opposite to the coolant (24).
 21. The heat exchanger according to claim 20, wherein the space (62; 162) hermetically closed off is filled with a gas under positive pressure in order to counteract the forces that act, as a result of a pressurized coolant (24), on the membrane (54; 154) and a seam (155) formed along a periphery of the membrane.
 22. The heat exchanger according to claim 1, wherein the heat exchanger is implemented as a flat-tube heat exchanger.
 23. The heat exchanger according to claim 1, further comprising a pressure measuring device, provided to measure the pressure in the coolant.
 24. The heat exchanger according to claim 1, further comprising a fill level indicator, provided to indicate the coolant fill level.
 25. The heat exchanger according to claim 1, for arrangement in a cooling circuit having a circulating pump (140), wherein the circulating pump has associated with it two filters (170), placed in series, that are arranged in the equalizing vessel (130′) of the heat exchanger (20).
 26. A heat exchanger having an equalizing vessel (110) for equalizing changes in the volume of a coolant in a coolant circuit, having at least one connector (64, 68; 112) for the inflow and/or outflow of coolant, and having a flexible diaphragm (54; 121; 154) arranged at a boundary between the coolant and an ambient gas.
 27. The heat exchanger according to claim 26, wherein the flexible diaphragm (121) is acted upon, in the direction toward the coolant, by a plunger (126) acted upon by a spring (124).
 28. The heat exchanger according to claim 27, further comprising a scale (130), or provided on the plunger (126).
 29. The heat exchanger according to claim 26, wherein the equalizing vessel (110) is joined to a heat exchanger (20) to form one module, and at least one filter (170) for filtering the coolant is arranged adjacent a boundary between heat exchanger (20) and equalizing vessel (110).
 30. A heat exchanger having an equalizing vessel for equalizing changes in the volume of a coolant in a coolant circuit, said equalizing vessel (110) being joined to the heat exchanger (20) to form one module, at least one filter member (170), through which coolant flows during operation, being arranged at a transition from the heat exchanger (20) to the equalizing vessel (110).
 31. The heat exchanger according to claim 30, wherein the filter member (170) is implemented as a plastic part, and is directly attached to a housing element (130′) of the equalizing vessel (120′).
 32. (canceled)
 33. The heat exchanger according to claim 26, further comprising a seal (44 a), which is joined to the filter (170) to form one module, provided between equalizing vessel (30; 130; 130′) and heat exchanger.
 34. The heat exchanger according to claim 33, wherein the filter (170) is joined to the seal (44 a) by one of injection-embedding and vulcanization. 